An efficient method based on machine learning for estimation of the wall parameters in through-the-wall imaging

The estimation of the wall parameters is important in through-the-wall radar imaging (TWRI). Ambiguities in the wall characteristics, including wall thickness, permittivity, and conductivity, will distort the imaging and shift the target position. To obtain a quick and accurate estimation of wall parameters, an efficient method based on machine learning is proposed. The estimation problem is converted to a regression problem. A map between wall parameters and the received signals is established and is regressed as a linear formulation after machine learning; in this manner, the wall parameters can be estimated in few seconds. The measurement results demonstrate that the estimated approach has the advantages of high precision and low computational time. The influence of the size, the location, the number of the targets and the length of the wall, the sampling interval, and noise on the estimation problems is discussed, and the image entropy is given to verify the effectiveness of the estimation values. The results based on support vector machines and least-square support vector machines (LS-SVMs), which are both machine-learning approaches, are compared. The comparison results reveal that the LS-SVM-based method can provide comparable performances in terms of accuracy and convenience but poor performances in terms of generalization and robustness.     

基于肖特基二极管改进模型的W波段宽带八次谐波混频器

在对肖特基二极管电磁模型和电路模型精确建模的基础上,设计并制作了W波段宽带八次谐波混频器.通过对肖特基二极管物理结构的分析,建立了其精确的三维电磁仿真模型和直到180 GHz的改进的宽带等效电路模型.针对W波段八次谐波混频器混频产物能量分布特点和工作带宽要求,设计了宽带射频和本振匹配网络,使混频器的工作带宽能覆盖整个W波段.测试结果显示,射频信号在75~110 GHz频率范围内,W波段八次谐波混频器最大变频损耗28 d B,最小变频损耗18 d B.     

基于Q-MMIC技术的W波段低成本PIN管开关

采用低成本方法设计了一款W波段单刀单掷开关。通过在单独加工的石英基片无源电路上安装倒装PIN管,获得了一款W波段准毫米波单片（Q-MMIC）开关。为了获得低损耗、高隔离度性能,开关设计中采用了3-D PIN管模型和电路补偿结构。测试结果表明开关在88GHz时插入损耗最小,最小值为0.5dB;在80-101 GHz频率范围内,开关导通时的插入损耗小于2 dB;在84-104 GHz频率范围内,开关隔离度大于30 dB。整个开关电路尺寸为1.5 mm× 3.0 mm。     

Ku波段宽带氮化镓功率放大器MMIC

基于0.25μm栅长GaN HEMT工艺,采用三级放大拓扑结构设计了一款Ku波段GaN功率放大器.放大器设计从建立大信号模型出发,输出匹配网络和级间匹配网络均采用电抗匹配减小电路的损耗,从而提高整体放大器的功率效率.测试结果表明,该放大器在14.6~18GHz频带内,小信号增益30dB,脉冲饱和输出功率达15W,功率附加效率(PAE)大于32%;在14.8GHz频点处,放大器的峰值功率达19.5W,PAE达39%.该结果表明GaN MMIC具有高频高功率高效率的优势,具有广阔的应用前景.     

抑制共模噪声的SIW 平衡馈电差分缝隙天线阵*

提出一种利用差分天线在共模激励和差模激励下方向图不同来抑制共模噪声的方法,并基于该理论 设计了6×6 平衡馈电差分SIW 缝隙天线阵进行验证。该天线由6个宽边纵向SIW 缝隙天线子阵列组成。辐射缝隙 被设计为只在差模激励下辐射,达到抑制共模信号的目的。每个天线子阵采用平衡差分馈电方式,使用两个1分6 梳状功分器将6个子阵同时激励。整个天线使用标准PCB 工艺加工,为了测试共模和差模激励,分别设计了带有 180°相移的功分器和T型功分器用来生成差模和共模信号。在差模激励下,天线的最大增益为20.2dBi,S11幅值小 于-10dB 带宽为7.2%(39.6 ~43.8GHz),在共模激励下天线的最大增益为10.1dBi,在整个工作频段内S11幅值大于 -7dB。仿真和实验结果验证了该结构的SIW 缝隙天线对差模信号能够有效地辐射而对共模信号进行抑制。     

Integrated chip-size antennas for wireless microsystems: Fabrication and design considerations

This paper reports on fabrication and design considerations of an integrated folded shorted-patch chip-size antenna for applications in short-range wireless microsystems and operating inside the 5–6 GHz ISM band. Antenna fabrication is based on wafer-level chip-scale packaging (WLCSP) techniques and consists of two adhesively bonded glass wafers with patterned metallization and through-wafer electrical interconnects. Via formation in glass substrates is identified as the key fabrication step. Various options for via formation are compared and from these, a 193 nm excimer laser ablation is selected for fabrication of the antenna demonstrator. The fabricated antenna has dimensions of 4 mm × 4 mm × 1 mm, measured operating frequency of 5.05 GHz with a bandwidth of ∼200 MHz at the return loss of −10 dB and a simulated radiation efficiency of 60% were achieved.     

A novel two-layer compact electromagnetic bandgap (EBG) structure and its applications in microwave circuits

Recently, photonic bandgap (PBG) structures have become one of the most interesting areas of research. These structures consist of one-, two- or three-dimensional finite periodically perforated dielectric/metallic material or ground planes that forbid the propagation of all electromagnetic waves within a particular frequency band (called the bandgap). This property permits additional control over the behaviour of electromagnetic waves. The research work was originally done in optical region, …     

快速PO-MoM技术分析电大载体线天线宽带特性

PO-MoM混合方法是研究电大尺寸载体上天线特性的有效方法。在应用PO-MoM分析复杂载体上天线宽频带电磁辐射问题时,由于需要在间隔很小的多个频率点进行填充阻抗矩阵的运算,计算过程耗时多,效率低。本文采用阻抗插值技术,通过构造有理插值函数来快速计算PO-MoM中的阻抗矩阵,并在迭代求解方程过程中采用了一种近场预条件技术,节省了计算时间,提高了计算效率。采用上述快速技术计算了垂直安装于平板的单极子天线和星载螺旋天线的宽带特性,并探讨了阻抗矩阵插值技术实现过程中一些参数的选取的问题。数值结果表明,结合阻抗插值矩阵插值技术并使用预条件技术的PO-MoM可以快速有效地分析大型复杂载体上天线的宽频带特性。     

An Alternative Method to Analyze Field Distribution in Curved Dielectric Waveguides

A simple and effective method is proposed to analyze the field distribution of a curved dielectric waveguide with rectangular cross-section. Numerical results are compared with the measured values. It is shown that the present approach is effective and reliable.